A CONTRIBUTION TO OUR KNOWLEDGE 

 OF THE ORIGIN OF THE BRITISH FLORA 



by 

 THEO, J. STOMPS. 



A lecture delivered lately by Dr. W. G. N. van 

 der Sleen at a meeting of the Royal Dutch Geogra- 

 phical Society on the so-called Cromer Forest Bed has 

 revived in this country the interest in an old theory, 

 advocated by Prestwitch, Harmer and others, ac- 

 cording to which many thousands of years ago, in an 

 âge when the North Sea was still land, the Rhine took 

 its course through the east part of England, entering it 

 near Walton on the coast of the county of Essex, to the 

 south of Harwich, and leaving England again after passing 

 in a northerly direction through Essex, Suffolk and Nor- 

 folk at Cromer on the north-coast of the last-named 

 county. With regard to this I hâve asked myself, whether 

 it would not be possible to find in the distribution of 

 certain species of plants in England and on the Continent 

 some arguments in favour of the above-mentioned theory, 

 upheld energetically by Van der Sleen. Any Dutch 

 botanist of expérience knows, that the valleys of our big 

 rivers Meuse and Rhine are characterized by certain 

 species of plants, which strictly foUow the beds of thèse 

 rivers, rarely-if ever-occur in other places and the distri- 

 bution of which is obviously dépendent on them. Ifitcould 

 be proved, that thèse species occur ail or partially in England 

 too, and this strictly locally in the counties of Essex, 



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